Stacking behavior of 2-D assemblies of octa-alkoxyl-substituted phthalocyanine studied by scanning tunneling microscopy

In this paper we report the observations of the bilayer structures of octa-alkoxyl-substituted phthalocyanine formed with high stability on graphite surfaces through direct deposition from solutions. The high resolution scanning tunneling microscope (STM) images of the overlayer assembly display discernible shifts. The bilayer structures are simulated by molecular mechanics method and the calculated results agree well with the experimental observations, indicating that the observed overlayer shift could be attributed to the π–π interaction associated with phthalocyanine. The results suggest that the multilayer growth of PcOC8 is jointly affected by π–π interactions, especially together with Van der Waals interactions.